The work attempts to elucidate brain structures involved in the regulation of sodium appetite, a model drive system, by studies of rats bearing stereotaxically induced brain lesions. The experiments are organized in a systematic manner to first identify critical structures and to subsequently elucidate their precise functions. The initial observations are made via standardized behavioral screening experiments. Phenomena uncovered in the screening experiments are then subjected to more detailed analysis and confirmation by special experiments specifically designed to answer particular questions. In addition, neuranatomical experiments are conducted to elucidate connections between critical structures with the ultimate aim of tracing relevant systems involving body fluid receptor mechanisms, gustatory processes, motivational and reinforcement functions, and sensory-motor integrative mechanisms for consummatory behavior. The brain structures to be studied in the proposed experiments are associated with the limbic-hypothalamic and the gustatory systems. These systems are thought to underlie two functions critical for normal regulation of sodium appetite -- homeostatic drive and gustatory discrimination and reinforcement.